<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .red{
            color: red;
        }
        .fontSize{
            font-size: 50px;
        }
    </style>
    <script src="./vue.js"></script>

</head>
<body>
    <!--模板-->
    <div id="demo">
        <span class="fontSize" :class='{red:addClass}'>hello,miaov</span>
    </div>
    <script>
        //数据
        let obj = {
            addClass:false
        };

        var vm = new Vue({
            el:"#demo",
            data:obj
        });

    </script>
</body>


</html>